willw2:

An investigation by The New York Times has found that in some towns, atrazine concentrations in drinking water have spiked, sometimes for longer than a month. But the reports produced by local water systems for residents often fail to reflect those higher concentrations.
Atrazine, which is sold under various brand names including AAtrex, is most commonly used on corn in farming states. But it can also be found on lawns, gardens, parks and golf courses. Sometimes, the only way to avoid atrazine during summer months, when concentrations tend to rise as cropland is sprayed, is by forgoing tap water and relying on bottled water or using a home filtration system.
Recent studies suggest that when adults and fetuses are exposed to even small doses of atrazine, like those allowed under law, they may suffer serious health effects. In particular, some scientists worry that atrazine may be safe during many periods of life but dangerous during brief windows of development, like when a fetus is growing and pregnant women are told to drink lots of water.